SC440A Datasheet, PDF (1/21 Pages) Semtech Corporation – High Effi ciency Integrated Driver for 6-Strings of 30mA LEDs

SC440A
POWER MANAGEMENT
High Efficiency Integrated Driver
for 6-Strings of 30mA LEDs
Features
Description
„ Wide input range 4.5V to 27V
„ 42V maximum output voltage with adjustable OVP for
smaller output capacitor
„ Drives up to 72 WLEDs in 6 strings
„ Programmable WLED current for up to 30mA per
string
„ 1% string-to-string current matching
„ 2A integrated power switch
„ Up to 91% efficiency
„ 0.2% to 100% PWM dimming
„ Analog dimming
„ 800KHz switching frequency for small external com-
ponent
„ Open/short LED protection
„ Short LED protection disable
„ <1uA shut-down current
„ Thermal protection
„ 4mm x 4mm x1mm MLPQ-24 package (Pb-free, Halo-
gen free, WEEE & RoHS compliant)
Applications
„ Medium-sized LCD panel
„ Notebook Display
„ White LED Power Supplies
„ Sub-Notebook and Tablet Computer Displays
„ Portable Media Players
„ LCD Monitors
„ Digital Video Cameras
Typical Application Circuit
The SC440A is a high-efficiency multiple string WLED
driver with an integrated boost converter. It operates
over a wide input range from 4.5V to 27V with a maximum
output voltage of 42V and a 2A internal power switch.
It can drive up to 42V output voltage in 6 strings with
current up to 30mA per string. The string-to-string current
matching is 1% typical, 3% maximum and the overall
efficiency is greater than 90% due to the low current sense
voltage and a low-impedance internal power switch. The
wide PWM dimming range boasts a ratio of 500: 1.
The 800kHz switching frequency enables the user to
optimize the external component sizes for high efficiency.
When there are fewer LEDs in each string, users can use
a lower output voltage protection level which yields an
allowable reduction in associated costs, size and voltage
ratings of the output capacitor.
The SC440A also features a comprehensive open and
short circuit LED protection functions. It disables the
corresponding strings with LED open or LED short
conditions while keeping other strings under normal
operation. This feature allows LCD panels to remain
viewable even under LED failure, wire disconnect, or short-
circuit conditions. The short LED protection function can
be disabled. The internal thermal shutdown protects the
IC from overheating at abnormal conditions. The SC440A
is available in a common 4mm x 4mm x1mm MLPQ-24
package.
Vin (4.5V -27V)
1
2
SW
VIN
SCP_EN
EN
SW
VOUT
OVPIN
6 Strings
FFLAG
OVPRTN
PWM _SC440A
12
6
IO1-6
COMP
IOSET
AGND
SS
EDP
PGND
IOGND
PGND
Jan. 12, 2010
www.semtech.com 1